1. Field of the Invention
The present invention relates generally to a display device using a single-panel diffractive light modulator and, more particularly, to a display device using a single-panel diffractive light modulator, in which a distortion correcting means is provided downstream of a projection unit, thus enabling correction of image distortion.
2. Description of the Related Art
With the development of microtechnology, Micro-Electro-Mechanical Systems (MEMS) devices and small-sized equipment, in which MEMS devices are assembled together, are attracting attention.
A MEMS device is formed on a substrate, such as a silicon substrate or a glass substrate, in microstructure form, and is a device in which an actuator for outputting mechanical actuating force and a semiconductor Integrated Circuit (IC) for controlling the actuator are electrically and mechanically combined with each other.
Recently, spatial light modulators using such MEMS devices have been developed. An example of such spatial light modulators is a Grating Light value (GLV) disclosed in U.S. Pat. No. 5,311,360 issued to Bloom et al., another example thereof is a light intensity conversion device for a laser display developed by Silicon Light Machine (SLM) Co., and still another example thereof is a diffractive light modulator developed by Samsung Electro-Mechanics Co. Display devices using such spatial light modulators are well known, and an example thereof is shown in FIG. 1.
FIG. 1 is a diagram showing the construction of a prior art display device using a single-panel diffractive light modulator.
Referring to FIG. 1, the prior art display device using a single-panel diffractive light modulator includes a light source unit 10, a condensing unit 12, an illumination unit 14, a diffractive light modulator 18, a Fourier filter unit 20, a projection unit 24, and a screen 28.
The light source unit 10 includes a plurality of light sources 11a˜11c. In one application thereof, the light sources 11a˜11c may be sequentially lit. The condensing unit 12 includes a mirror 13a and a plurality of dichroic mirrors 13b and 13c, and functions to cause light from the plurality of light sources to have a single light path by combining the light from the plurality of light sources 11a˜11c. 
The illumination unit 14 converts light, passed through the condensing unit 12, into linear collimated light, and causes the linear collimated light to be incident on the diffractive light modulator 18. The diffractive light modulator 18 generates linear diffracted light having a plurality of diffraction orders by modulating the incident light, and emits the linear diffracted light. In this case, diffracted light, which has a given diffraction order and is desired to be used in an application, is formed to vary in light intensity at respective locations thereof so that it forms images on the screen 28. That is, since the diffracted light created in the diffractive light modulator 18 is linear and the linear diffracted light may have different light intensity values at respective locations thereof, two-dimensional (2D) images can be formed when the diffracted light is scanned over the screen 28.
Meanwhile, the diffracted light generated by the diffractive light modulator 18 enters the Fourier filter unit 20. The Fourier filter unit 20 includes a Fourier lens 21 and a dichroic filter 22, and functions to separate the diffracted light according to diffraction order and to pass only diffracted light having a desired diffraction order therethrough.
Meanwhile, the projection unit 24 includes a projection lens 25 and a scanner 26. The projection lens 25 expands the incident diffracted light, while the scanner 26 forms images by projecting the incident diffracted light onto the screen 28.
Meanwhile, according to the above-described prior art, diffracted light is projected directly on the screen 28 by the projection unit 24, so that the projection distance from the scanner 16 to the center A of the screen 28 in a lateral direction (scanning direction) and the distance from the scanner 16 to each side edge A′ of the screen 28 in the lateral direction are different, with the result that a distorted image is formed on the screen 28, as shown in FIG. 2A. In more detail, when, in FIG. 1, the projection distance from the scanner 26 to the center A of the screen 28 in the lateral direction is compared with the projection distance from the scanner 26 to the side edge A′ of the screen 28, the projection distance for the side edge A′ is longer than the other distance by distance a, therefore distortion occurs, as shown in FIG. 2A. When the screen 28 is viewed from the front thereof and an imaginary plane 28′, defined by the same projection distance, is considered, as shown in FIG. 2B, it can be seen that a longer projection distance is required for diffracted light to reach the side edge A′ of the screen 28 from the scanner 26. As a result, the diffracted light travels a longer projection distance, so that an image is vertically expanded, with the result that distortion shown in FIG. 2B occurs.